We propose to test the efficacy of an innovative multi-session motivational/educational intervention for reducing exposure of sexually active adolescents to human immunodeficiency virus (HIV). Subjects will be consenting adolescents (ages 14-20 years) who present for medical care related to sexual activity at the Planned Parenthood clinic of Santa Cruz (California). The motivational/educational strategy will employ techniques based on social learning theory and social marketing; including peer group support sessions, use of video role modeling and media presentations designed to increase perception of personal risk and to change perceptions of normative behavior. A major focus will involve teaching adolescents how to negotiate safe sex (including abstinence). The comparison (usual care) intervention will employ brief intervention methods delivered by Planned Parenthood personnel including counseling and distribution of educational materials. Outcome assessment will be: (a) a biological index of genital mucosal contact generated by surveillance data on the prevalence and incidence of pregnancy and several sexually transmitted diseases (human immunodeficiency virus, herpes simplex type II, cytomegalovirus, human papilloma virus, Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, and bacterial vaginosis (b) self-reports of high risk behavior and, (c) subjects' responses on scales assessing perceived susceptibility, self efficacy, knowledge, perception of peer norms, and anxiety regarding AIDS. The study will provide an assessment of innovative prevention techniques and the impact of other diseases that share modes of transmission with AIDS. The study will also generate information on the characteristics of adolescents with differing responses to the study interventions. The Santa Cruz Clinic is typical of many such clinics in the U.S. The results of this study will be generalizable to a group of adolescents at highest risk for HIV and other STDs, namely those who are sexually active and who may not be reached in school settings. An effective treatment for AIDS is not yet available and release of a vaccine is not anticipated in the next five years. Control of the AIDS epidemic must occur through prevention of transmission of the etiologic agent of AIDS (HIV), which occurs through sexual contact, through blood contact and via perinatal exposure.